The majority of bacterial infections (65 percent) involve growth of the organisms as surface-adherent, biofilms. Within biofilms bacteria are protected from a number of stresses such as antimicrobial agents, nutrient fluctuation, and host defenses. While a number of studies have identified genes involved in the early stages of biofilm formation, very little is known about the physiology and gene expression of established biofilms. The present study will employ gene array technology to identify the genes that are being expressed in young, mature, and aged E. coil biofilms as previous studies have shown that antibiotic resistance increases with biofilm age. This is an exciting concept in that we can simultaneously determine and compare the use (expression levels) of all 4290 genes in E. coil during growth as attached (biofilm) and free-swimming (planktonic) forms. During the first part of this project, we will grow bioflims and planktonic E. coli at two different growth rates, using a continuous culture device (chemostat). In this fashion, we will be able to control the growth rate of the biofilm-forming bacteria. At various times, RNA will be extracted from the biofilm and planktonic populations, purified and used to produce labeled cDNA that can then be bound (hybridized) to a commercially available gene array. Analysis of the binding intensity will give an indication of the use (expression) of each gene. In the second part of this project, we will use this approach to investigate differences in gene expression in E. coil that lack the ability to grow slowly or survive starvation. Both of these characteristics (slow-growth and starvation survival) are considered to be necessary for biofilm formation. Overall, this project will explain several fundamental aspects of E. coli biofilm growth and suggest possible targets for future antibiotic research.